Information filtering means information processing for automatically selecting information according to whether the information matches a request prescribed by the user (filtering condition) or not. In the information filtering, in order to improve filtering precision, it is generally done to use automatic document classifying technique by mechanical learning, and to add or change filtering condition by feedback specified by the user (Patent Document 1). This is called as a learning filter.
Further, as a method to improve filtering precision, there is another filtering method which combines plural learning filters having different filtering conditions (Patent Document 2). In this method, outputs from the plural filters (degree of conformance to the filtering condition) are composed based on the specification by the user to make the final output.    Patent Document 1: JP9-288683A    Patent Document 2: JP2001-229164A